I tried making users able to mount usb (i fallowed some guild that involved AMD)
In the end i gave up....

sudo is really the best and easy to implement solution of the problem.

Just what I wanted to know, that it is not working for others too.

OK what I need to do apart for installing sudo, also what is the difference between sudo and su? Asking because from what I remember from my Ubuntu experience we use sudo followed by some command and then we need to enter the password. If there is no escape from entering password then why not use "su".

you need to fetch moment when /dev/daX is created and then change permissions for it, so user can access it (otherwise by default it's root/wheel)....
That's the hard part....
that's why simply giving user permissions to write to /mnt/usb won't work.